It is a well-known principle that every action has is an equal and opposite reaction (Newton's Third Law). Thus, for a hammer, when the impact surface of the hammerhead impacts a target, the hammer is jolted backwards due to the reaction caused by the hammerhead striking its target. This opposite reaction is commonly referred to as hammer recoil.
For minimizing or eliminating hammer recoils, which cause vibrations and injuries to the user, numerous hammers were invented. Broadly speaking, these hammers utilize some form of inserts placed in a hollow chamber within the hammerhead, or within a separate hollow body having a hollow chamber attached to the hammerhead. The inserts are configured to move from a rear surface of the hollow chamber to a front surface of the hollow chamber. Accordingly, when the hammer moves in a first direction to impact its target, the inserts are pushed by the rear surface of the hollow chamber to move in the same first direction.
As the impact surface of the hammerhead impacts a target and starts its recoil in a second direction, the inserts still move in the first direction within the hollow chamber and impact the front surface of the hollow chamber, in the first direction. The inserts impacting against the front surface of the hollow chamber thus cancel the recoil in total or substantially. The amount of cancellation depends, in part, on the weight percentage of the inserts compared to the weight of the hammerhead. Without being restricted to any particular theory, the deadblow impact or feel to the user also depends on the distance the insert travels before it impacts the front surface, which will influence how far the hammer recoils before the insert impacts the front surface to cancel out the effect.
U.S. Pat. No. 6,234,048 to Carmien discloses a non-recoil hammer, with a hammerhead that has an open socket for receiving a separate hollow canister. The hollow canister connects to a tool handle and contains a relatively high mass moveable filler material in a hollow chamber, such as steel shot pellets. The hollow canister is received within the open socket to form a completed hammer. Due to the two-piece design, the hammer is more complicated and costly to manufacture.
U.S. Pat. No. 5,916,338 to Bergkvist et al. discloses a hammer having a hammerhead with an impact element and a cavity at least partially filled with particulate material, such as steel shot, so as to dampen the recoil of the hammer. The impact element is forged with the head as a single piece or may be formed as a separate part that is connected to the head by welding. However, since the cavity extends the full length of the hammerhead, the handle cannot attach to the hammerhead by passing through central portion of the hammerhead, but is attached via partial through hole at the central portion of the hammerhead. This makes the handle more susceptible to slippage or separation from the hammerhead. Furthermore, because of the cavity, a conventional handle with a split end for wedging the handle with a wedge is not useable with the disclosed hammerhead.
U.S. Pat. No. 4,039,012 to Cook discloses a non-rebound hammer having a hammerhead portion with forwardly and rearwardly facing metallic impact surfaces. The head portion contains a hollow cylindrical core for receiving a quantity of pellets, such as small lead shots. The hammerhead also contains a core hole for receiving a handle rod. The handle rod and the hammerhead are then co-molded with an encasement. Due to the co-molded configuration, the entire hammer must be discarded when damage is done to the handle.
U.S. Pat. No. 2,604,914 to Kahlen discloses a hammerhead having a rebound-preventing means. The hammerhead has a body with a striking head at each end of the body. Each striking head is formed integrally with the body, or alternatively it may be secured to the body as a separate piece. A chamber is formed in the body immediately behind the striking heads. The chamber contains irregularly shaped particles 26, as shown in FIG. 3 of the '914 patent. The particles almost completely fill the chamber, with the total weight of the particles dependent on the recoil quality of the striking head, the size of the hammer, and the weight of the head. Due to the lengthwise chamber, a ferrule is used to connect a handle to the body. This makes the body unnecessarily bulky.
There is therefore a need for a non-recoil hammer or deadblow hammer that minimizes or negates the effects of hammer recoils and that do so without the shortcomings of prior art deadblow hammers. Additionally, there is also a need for a method of making the desired deadblow hammer.